Instruction

Scientists count about 3,000 natural minerals, and every year this number is replenished with new species. But only one hundred of them are widely distributed and used in various fields of production. In the Stone Age, silicon was used as a tool of labor, and the jewelry industry at all times would not have been so diverse without this material.

Amethyst, agate, ruby, turquoise, lapis lazuli, garnet, moonstone, opal, amber are a small list of popular minerals known as gems.

Diamond, which is translated from Greek as “irresistible, unsurpassed”, is the hardest and most durable among all minerals. It leaves scratches on any stones and, and nothing can scratch it. Due to this property, diamond is used in the mining industry. In jewelry production, a diamond is given a special brilliant cut, thanks to which this mineral begins to reveal its optical properties to the maximum. A diamond is the most expensive gemstone, measured in carats. Most often, diamonds are colorless and transparent, but they can also have shades of various colors - from yellow to black and brown. The largest diamonds are given names and become historic stones.

Pearls are a waste product of molluscs, arising from the deposition of layers of aragonite around a center in the shell mantle. Such a center may be a grain of sand or another foreign object. The color of pearls varies from snow white to black or greenish. It depends on impurities in aragonite and other factors. Depending on the size, pearls are divided into varietal, beads and pearl dust. The shape of this mineral is also varied. Large beads of the correct spherical shape are valued.

Malachite is one of the most beautiful minerals. Its color can contain the entire palette of green tones - from light green or turquoise to rich dark green, close to black. Malachite is a very common ornamental stone. Due to its softness, this mineral serves as the basis for vases, figurines, caskets and other souvenirs, and is also widely used in the jewelry industry. Malachite amulets and talismans have been popular since ancient times. The ancient Greeks decorated the facades of buildings with this material, and the Egyptians used malachite powder as an eyeliner.

Rock crystal, jasper, cat's and tiger's eye, chalcedony, citrine, flywheel and other precious stones are a variety. This mineral can have a different color and color density. For example, opaque red-green jasper and sparkling lemon yellow citrine. Transparent quartz is widely used in optics, radio engineering, acoustics and other areas of production and jewelry.

Amber is a fossil coniferous tree, its main deposit is considered to be the Baltic coast. This mineral has a number of healing properties, due to which it is very common in the production of talismans, jewelry, amulets. In the era of the Roman Empire, its value was equal to gold.

The solid shell of the Earth - the earth's crust - is only 1.5% of the total volume of the globe. But, despite this, it is the earth's crust, or rather its upper layer, that is of greatest interest to us, since it is a source of mineral raw materials.
Minerals- These are relatively homogeneous natural bodies with certain chemical composition and physical properties. The name "mineral" comes from the Latin word "minera", which literally means - ore, ore. The science that studies the composition, structure and properties of minerals, their origin and conditions of occurrence is called mineralogy.
Minerals are formed as a result of physical and chemical processes occurring in the earth's crust. Like all the nature around us, they are made up of chemical elements. Figuratively speaking, a mineral is a kind of building made of bricks - chemical elements, built according to certain laws of nature. And just as a lot of different buildings were erected on Earth from approximately the same number of bricks, more than 3 thousand various minerals were created by nature in the earth's crust from a relatively small number of chemical elements.

In total, taking into account the numerous varieties, there are more than 7 thousand of their names, which are given to each mineral on some basis.
In the earth's crust, minerals are more often found not independently, but in composition. They largely determine the physical and mechanical properties of rocks and, from this point of view, are of the greatest interest for stone processing technology.
Most minerals occur naturally in the solid state. Solid minerals can be crystalline or amorphous, differing in external geometric shape - regular for crystalline and indefinite for amorphous.

The shape of the minerals depends from the arrangement of atoms in them. In crystalline minerals, atoms are arranged in a strictly defined order, forming a spatial lattice, due to which many minerals (for example, a quartz crystal) look like regular polyhedra. Crystalline minerals are anisotropic, that is, their physical properties are different in different directions. In amorphous minerals (usually they are in the form of deposits), the atoms are arranged randomly. Such minerals are isotropic, that is, their physical properties are the same in all directions.

Mineral classification

In accordance with the currently generally accepted chemical classification, all minerals can be divided into nine classes:
I. Silicates - salts of silicic acids, among which there are subgroups of minerals that have some common composition and structure: feldspars, divided by chemical composition into plagioclases and orthoclases, pyroxenes, amphiboles, micas, olivine, talc, chlorites and clay minerals. This is the most numerous class, numbering up to 800 minerals.
II. Carbonates - salts of carbonic acid, including up to 80 minerals, including the most common calcite, magnesite and dolomite.

III. Oxides and hydroxides - combine about 200 minerals, among which the most common are quartz, opal, limonite, hamatite.
IV. Sulfides are compounds of elements with sulfur, numbering up to 200 minerals. A typical representative is pyrite.
V. Sulphates - salts of sulfuric acid, including about 260 minerals,
among which the most widespread are gypsum and anhydrite.
VI. Halides - salts of halogen acids, numbering about 100 mines
rals. Typical representatives of halides are halite (table salt) and
fluorite.
VII. Phosphates are salts of phosphoric acid. Typical representative -
apatite.
VIII. Tungstates are tungstate compounds.
IX. The native elements are diamond and sulfur.

Minerals are also considered some natural substances that are liquids under normal conditions (for example, native mercury, which comes to a crystalline state at a lower temperature). Water, on the contrary, is not classified as a mineral, considering it as a liquid state (melt) mineral ice.

Some organic substances - asphalt, bitumen - are often mistakenly classified as minerals, or they are classified as a special class of "organic minerals", the expediency of which is very controversial.

Some minerals are in an amorphous state and do not have a crystalline structure.

This applies mainly to the so-called metamict minerals, which have an external form of crystals, but are in an amorphous, glassy state due to the destruction of their original crystal lattice under the influence of hard radioactive radiation from the radioactive elements (U) included in their own composition. Minerals are clearly crystalline and metamict minerals that have the external form of crystals, but are in an amorphous, glassy state.

“A mineral is a chemically and physically individualized natural physical and chemical reaction, which is in a crystalline state” (Godovikov A.A., “Mineralogy”, M., “”, 1983).

According to the definition of academician N.P. Yushkin (1977), “minerals are natural discrete organically integral systems of interacting atoms ordered with a three-dimensional unlimited periodicity of their equilibrium positions, which are relatively indivisible structural elements of rocks and dispersed formations. The whole set of minerals constitutes the mineral level of the structural company of inorganic matter, the specificity of which is the crystalline state, which determines the properties, laws of functioning and methods of studying mineral systems.

The concept of "mineral" is often used in the meaning of "mineral species", that is, as a set of mineral bodies of a given chemical composition with a given crystalline structure.

The crystal structure is both the most important diagnostic characteristic of the mineral and the carrier of the genetic information embedded in the mineral, which, among other things, is deciphered by mineralogy. The question of the expediency of classifying certain non-crystalline products as minerals as “exceptions to the rule” is controversial and is still being discussed by scientists. At the same time, modern research has shown that some amorphous, as previously thought, geological products are more complex than previously thought and have an internal “long-range order structure”.

Colloidal phases exist only as intermediates in processes mass transfer and mineral formation and are one of the physico-chemical environments in which or from which minerals crystallize.

Mineral is

Mineral classification

Attempts to systematize minerals on a different basis were already made in the ancient world. Initially (from Aristotle to Sina and Biruni) they were divided according to external features, sometimes involving genetic elements, often the most fantastic. From the late Renaissance to the beginning of the 19th century. classifications based on external signs and physical properties of minerals dominated. In the second half of the 19th - early 20th centuries. The chemical classifications of minerals (the works of P. Grot, V. I. Vernadsky, and others) have become exceptionally widespread. From the 20s. 20th century an increasingly important role is played by crystal-chemical classifications, in which the chemical composition and crystal structure of minerals are equally taken as the basis. In modern mineralogy there are many different variants of mineralogical systematics. In the most common classification of minerals into types and classes according to chemical composition.

Smaller taxa within classes (subclasses, divisions, groups, etc.) are distinguished according to the type of structure (silicates) and in accordance with the degree of compositional complexity. When distinguishing fractional taxa, they are also based on the grouping of cations and anions that are close in geochemical and crystal chemical terms. Special studies are being carried out in the direction of creating a natural genetic-structural and chemical-structural systematics of minerals.

There are many classifications of minerals. Most of them are built according to the structural-chemical principle.

By prevalence, minerals can be divided into rock-forming - forming the basis of most rocks, accessory - often present in rocks, but rarely constituting more than 5% of the rock, rare, occurrences of which are single or few, and ore, widely represented in ore deposits.

The most widely used classification is by chemical composition and crystal structure. Substances of the same chemical type often have a similar structure, so minerals are first divided into classes according to their chemical composition, and then into subclasses according to structural features.

The currently generally accepted crystal-chemical classification of minerals divides all of them into classes and looks like this:

native elements.

These are minerals that are made up of one element. Although they are rare and make up only 0.1% of the weight of the earth's crust, their importance to humans is great. It is enough to list the representatives of this group:

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Mineral is

It is much less common in native form, which is more likely to form chemical compounds. Nuggets of rare metals are extremely rare in nature: palladium (Pd), osmium (Os), iridium (Ir). Most of the minerals of this group occur predominantly or only in native form (Au, Ag, Pt, Pd, Ir, Os). The origin of almost all native elements is endogenous, most often hydrothermal. The exception is sulfur which can be either endogenous or exogenous. Separately, native carbon is considered, which forms two basic polymorphic modifications: diamond and graphite. Diamond is formed as a result of magmatic processes; it is most commonly found in kimberlites.

Graphite is formed from sedimentary rocks rich in organic matter as a result of metamorphic processes.

II. Section Sulfides, sulfosalts and similar compounds.

1. Class Sulfides and similar compounds.

2. Class Sulfosalts.

The section under consideration includes sulfur, selenium, telluride, arsenic and antimony compounds. metals. These include a very significant amount of industrially important minerals that play a significant role in the composition of numerous deposits of metallic minerals.

The largest number of minerals is represented by sulfur compounds (sulfides, sulfosalts). All of them, with the exception of hydrogen sulfide, are distributed in nature in the solid state.

III. Section Halogen compounds (Halides).

1. Fluoride class.

2. Class Chlorides, bromides and iodides.

Starting with this type of compounds, we will deal with minerals that differ sharply in their properties from those considered.

In the vast majority, these will be compounds with a typical ionic bond, which determines completely different properties of minerals. The most prominent representatives of them are halogen compounds metals.

From a chemical point of view, the minerals related to this are represented by acid salts: HF, HCl, HBr and HJ; accordingly, among these minerals, fluorides, chlorides, bromides and iodides are distinguished.

IV. Section Oxides and hydroxides.

1. Class Oxides.

2. Class Hydroxides.

This class includes minerals, which are compounds of various elements with oxygen, and hydroxides also contain water. By the number of minerals included in it, it is in one of the first places, it accounts for about 17% of the mass of the entire earth's crust (of which silicon oxides account for about 12.5% ​​and iron oxides - 3.9%). Minerals of this class are formed under both endogenous and exogenous conditions.

Luster glassy, ​​greasy in the break. Solid. Colorless, white, greyish, smoky black, pink, purple, green. Doesn't give a trait. Cleavage is absent. The break is uneven. Solid dense, loose (quartz sand); in addition, inclusions, individual crystals or druses. The crystals are shaped like a hexagonal prism topped with a pyramid. The crystal faces are covered with transverse hatching. Syngony is trigonal. Crystals overgrown or ingrown. In Kazakhstan, a rock crystal was found the size of a two-story house, its weight is 70 tons.

In areas where sands are distributed (in deserts), there are crystals and druses of gypsum (pseudomorphoses of quartz after gypsum), penetrated by grains of sand, which gives these formations a greater hardness that is not inherent in gypsum.

V. Section Oxygen salts (hydroxy salts).

1. Class Nitrates.

2. Class Carbonates.

3. Class Sulphates.

4. Class Chromata.

5. Tungsten class.

6. Class Phosphates, arsenates and vanadates.

7. Borata class.

8. Class Silicates.

A. Island silicates.

B. Chain silicates.

B. Ribbon silicates.

D. Layered silicates.

D. Framework silicates.

Among the salts, first of all, there are anhydrous and aqueous salts (i.e., containing H2O molecules in their composition).

VI. Section Organic compounds.

In the taxonomy of minerals, the class Organic minerals, as it were, stands apart from others, since the products included in it, although they are natural chemicals with a fairly definite constant composition and properties, are devoid of a crystalline structure.

They cannot be characterized from a crystal-chemical point of view, but traditionally belong to minerals, having much more similarities with them than differences. Note, however, that this is not all natural organics, and the assignment to this section of each specific natural organic goods requires a thoughtful and responsible approach.

Structure and chemical composition of minerals

Depending on the chemical composition of minerals and physicochemical parameters, there is a type of chemical bond between individual elements and, as a result, the regularity of their spatial distribution in the crystal structure of minerals.

A significant change in composition causes a change in structure and a transition to a substance with a new structure, i.e. to another mineral. The usual deviations of the real structure of minerals from the ideal are in individual nodes of the crystal lattice, associated with the appearance, for example, of impurities in interstices, a change in the valency of some of the cations (anions).

As a result of various defects (vacancies, impurity, radiation and other defects, the entry of foreign ions or molecules, such as water into channels and other cavities of the lattice, changes in the charge of cations and anions, etc.) and dislocations, mineral crystals can acquire a block structure. Real minerals sometimes form the so-called. ordering series (for example, feldspars), when the distribution of various cations over structural positions deviates to some extent from the correct order inherent in ideal crystals, and tends to order with decreasing temperature.

No less widespread are the phenomena of decomposition of solid solutions (mixed crystals), which find expression in the specific structures of minerals.

Minerals with layered crystal lattices (for example, micas, molybdenite, sphalerite, clay minerals, chlorites, graphite, etc.) are characterized by the phenomenon of polytypy, in which adjacent layers (or stacks of layers) turn out to be somewhat rotated relative to each other.

As a result of such a rotation, modifications (or polytypes) arise, the elementary cells of which have the same parameters along two axes and different parameters along the third. The formation of polytypes is explained by the conditions of crystal growth (in particular, kinetic factors and the mechanism of helical growth).

In the case of isomorphic series, when separating mineral species, they are guided by the following rules: in two-component (binary) solid solutions, two mineral species are distinguished (with a content of end members from 0 to 50 and from 50 to 100 molecular %), in three-component ones - three. Earlier, in binary isomorphic mixtures, three mineral species were distinguished, the names of which were fixed in the mineralogical nomenclature.

Along with this, in mineralogy there are some other principles for distinguishing mineral species. So, if the representatives of this series are of particular importance in terms of distribution and individual intermediate members of the series of solid solutions are typical for certain parageneses, the allocation of a mineral species becomes fractional and is often based on a number basis. An example is plagioclases, among which albite is distinguished.

Crystals of real minerals often show a zonal or sector, block or domain structure; isomorphic impurities can be distributed in them statistically (randomly), occupy strictly defined structural positions, or be grouped into clusters; the inclusion of impurity components in the form of flat inclusions into minerals, etc. was found.

The study of the real structure and composition of mineral crystals provides important information about the conditions of mineral formation.

Chemical composition and, chemical and crystal chemical formulas. The composition of minerals includes all stable and long-lived isotopes of elements of the periodic system, except for inert gases (helium and argon can accumulate in structural channels and cavities of crystal lattices of minerals as radiogenic products or due to capture from the atmosphere). But the mineral-forming role of various elements is not the same. Impurities can enter minerals not only isomorphically, but also by sorption, and also in the form of mechanical mineral or gas-liquid microinclusions. These rows (series) define the boundaries of variations in the composition of minerals, and thus the fluctuations in their physical properties: density, hardness, optical, magnetic and other parameters of the elementary cell, melting temperature, etc.

About 25% of the total number of mineral species in the earth's crust are silicates and aluminosilicates; about 18% are phosphates, arsenates and their analogs, about 13% are sulfides and their analogs, about 12% are oxides and hydroxides. Minerals belonging to other classes of chemical compounds make up about 32%.

In terms of abundance in the earth's crust, aluminosilicates (especially feldspars) and silicates sharply dominate, followed by oxides (primarily quartz) and hydroxides, and then carbonates; in total, they make up about 98% of the upper part of the earth's crust (down to a depth of 16 km).

The composition of minerals is expressed by its chemical formula - empirical, semi-empirical, crystal chemical. The empirical formula reflects only the relationship between the individual elements in minerals. In it, elements are arranged from left to right as the number of their groups in the periodic system increases, and for elements of the same group, as their serial numbers decrease, i.e. as their strength increases.

Elements that form isomorphic mixtures are given in parentheses separated by commas, arranged depending on their content in minerals. After deciphering the crystal structures of the vast majority of minerals and clarifying the positions of various elements in their crystal lattice, it became possible to introduce into mineralogy the concept of the basic Law of the state of minerals, in which the chemical composition of minerals is closely linked to their structure. Expression fundamental law of the land minerals serve as so-called. structural, or crystal chemical formulas, compiled and written according to certain rules. In these formulas, elements playing the role of normal cations are written at the beginning in the same order as in empirical formulas.

The rapid crystallization of minerals leads to a distortion of the shape of their crystals, the emergence of skeletal, dendritic, filamentous forms.

Mineral crystals often have characteristic shading on their faces, figures of growth and dissolution. Mass crystallization (for example, during the formation of igneous rocks) creates an environment of constrained growth, and the minerals form grains of irregular shape.

Mineral individuals and mineral aggregates compose mineral bodies.

Properties of minerals

The physical properties of minerals are determined by their internal structure and chemical composition. The fluctuations in physical properties observed in real minerals are caused by isomorphism phenomena, structural defects, varying degrees of order (sometimes even within the same grain), and other factors. The physical properties of minerals, along with their morphology, are the basis for their diagnostics, searches, and, in some cases, their practical use.

By density, minerals are divided into light (up to 2500 kg / m3), medium (2500-4000 kg / m3), heavy (4000-8000 kg / m3) and very heavy (more than 8000 kg / m3). The density of minerals is determined by its composition (content of heavy cations) and the type of structure, the degree of its perfection.

Mechanical properties include mineral hardness, elastic properties, fracture, mineral cleavage, and looseness. The qualitative determination of the elastic properties of minerals is carried out visually, according to their response to mechanical stresses (the nature of deformations).

There are brittle (most) and malleable (some native metals and sulfides) minerals, and among sheet and scaly minerals - flexible elastic (micas) and inelastic, as well as inflexible (brittle micas). Fibrous minerals are brittle and flexible (chrysotile asbestos).

Fracture is an important diagnostic property of a mineral; it characterizes the surface of the fragments into which it splits (not along cleavage) upon impact. Preliminary field diagnostics of minerals is carried out according to external signs and simple physical properties: morphology of segregations, relative hardness and density, line color, gloss, tint, cleavage, fracture, luminescence, etc.

For the determination of carbonates, staining methods, "boiling" with HCl, are used. Sometimes they resort to the simplest qualitative chemical reactions (for example, for phosphorus with ammonium molybdate). Many common minerals, rock-forming and ore, can be determined quite reliably already in the field.

Highly dispersed minerals, such as clay, which give fuzzy diffuse lines on x-rays, are confidently diagnosed only under an electron microscope, using the electron diffraction method. The same method makes it possible to accurately diagnose minerals, polytypes of foliated and scaly minerals. Carbonates and other minerals containing volatile components are determined using thermal analysis.

The most important characteristics of minerals are crystal chemical structure and composition. All other properties of minerals follow from them or are interconnected with them. The most important properties of minerals that are diagnostic features and allow them to be determined are as follows:

Crystal habit. It turns out during visual inspection, a magnifying glass is used to examine small samples

Hardness. Determined by the Mohs scale.

Glitter is a light effect caused by the reflection of part of the light flux incident on a mineral. Depends on the reflectivity of the mineral.

Cleavage - the ability of a mineral to split along certain crystallographic directions.

Fracture is a specific feature of the mineral surface on a fresh non-cleavage cleavage.

Color is a sign that definitely characterizes some minerals (green malachite, blue lapis lazuli, red cinnabar), and is very misleading in a number of other minerals, the color of which can vary over a wide range depending on the presence of impurities of chromophore elements or specific defects in the crystal structure ( fluorite, quartz, tourmaline).

Streak color is the color of a mineral in a fine powder, usually determined by scratching the rough surface of a porcelain biscuit.

Brittleness - the strength of mineral grains (crystals), which is found during mechanical splitting. Fragility is sometimes linked or confused with hardness, which is incorrect. Other very hard minerals can easily split, that is, be brittle (for example, diamond).

Obtaining objective quantitative data on the genesis of minerals makes it possible to reconstruct the geological processes and the history of the formation of mineral deposits, i.e. to create a scientific basis for their search, exploration and industrial evaluation.

Application

Approximately 15% of all known mineral species are used in engineering and industry. Minerals are of practical value as sources for obtaining all metals and other chemical elements (ores of ferrous and non-ferrous metals, rare and trace elements, agronomic ores, raw materials for chemical industry). The technical application of many minerals is based on their physical properties.

Hard minerals (diamond, corundum, garnet, agate, etc.) are used as abrasives and anti-abrasives;

minerals with piezoelectric properties (quartz, etc.) - in radio electronics;

micas (muscovite, phlogopite) - in electrical and radio engineering (due to their electrical insulating properties);

asbestos - as a heat insulator;

talc - in medicine and in lubricants;

quartz, fluorite, Icelandic spar - in optics;

quartz, kaolinite, potassium feldspar, pyrophyllite - in ceramics;

magnesite, forsterite - as magnesian refractories, etc.

A number of minerals are precious and ornamental stones. Mineralogical prospecting and evaluation of mineral deposits are widely used in the practice of geological exploration.

The differences in the physical and chemical properties of minerals (density, magnetic, electrical, surface, radioactive, luminescent and other properties), as well as color contrasts, are the basis for the methods of ore dressing and separation of minerals, as well as geophysical and geochemical methods for prospecting and exploration of mineral deposits.

On a large scale, industrial synthesis of single crystals of artificial analogues of a number of minerals is carried out for radio electronics, optics, abrasive and jewelry industry.

To date, more than 4 thousand minerals are known. Every year, several dozen new mineral species are discovered and several are “closed” - they prove that such a mineral does not exist.

Four thousand minerals is a very small number compared to the number of known inorganic compounds (more than a million).

Sources

Wikipedia - The Free Encyclopedia, WikiPedia

geoman.ru - Library about nature and geography

mining-enc.ru - Mining encyclopedia

xumuk.ru - Site about chemistry

agrofak.com - Assistant agronomist

iznedr.ru - From bowels Earth

webois.org.ua - Portal about stones and minerals

catalogmineralov.ru - Catalog of minerals

Encyclopedia of the investor. 2013 .

The composition of minerals includes most of the chemical elements of the periodic system. There are species-forming elements - Si, O, H, Al, Ca, Na, Mg, Cu, Pb, S, etc. Minerals are represented by the following main types of chemical compounds: simple substances or native elements - native sulfur, graphite, native copper, gold, platinum, etc.; oxides and hydroxides: corundum Al2O3, rutile TiO2, cuprite Cu2O, etc.; salts of various oxygen-containing and anoxic acids: halite NaCl, pyrite FeS2, calcite CaCO3, barite BaSO4, etc. Many salts are characterized by complex anions (radicals): in silicates 4+, in carbonates [CO3] 2-, in phosphates [PO4] 3-, etc. The ability of minerals to form compounds of variable composition is called isomorphism (Greek "isoa" - the same; "morpho" - form), which consists in the mutual substitution of atoms and ions in the crystal lattices of minerals without disturbing their structure. Isomorphism is due to the proximity of the properties of atoms and ions, as well as the influence of temperature, pressure, and the concentration of components. Example. An isomorphic series of a group of plagioclases (cl. silicates and p/cl. feldspars), the extreme members of which are albite Na and anorthite Ca.

11. Physical properties of minerals.

1. Color - color of minerals m. b. several types:

- idiochromatic- characteristic of the mineral (malachite, turquoise);

- allochromatic- introduced by impurities of other minerals or gas inclusions (carnelian, rose quartz);

-pseudochromatic- false coloration caused by the interference of light rays (irisation, tint);

Irisation- pseudocolor, which occurs inside the crystal. Irization (from the Greek íris - rainbow), an optical phenomenon consisting in the appearance of an iridescent play of colors on the faces and cleavage planes of certain minerals (for example, calcite, labrador, opal, etc.) during the passage of light.

discoloration- a thin iridescent film on the surface of the mineral, which differs sharply from the color of the rest of its mass. The reason for P. is the presence on the surface of mineral grains of thin films formed as a result of its change (for example, under the influence of oxygen) and causing an iridescent light effect (see Irization). It is characteristic of bornite, chalcopyrite, limonite, and others. On a fresh surface, no mineral fracture is observed.

2. The color of the line is the color of the fine powder of the mineral left by it when scratched on an unglazed porcelain plate (biscuit). Tv-t on the Maos scale (5-6) 6-7. The trait does not match: pyrite is brass-yellow in color, the color of the trait is black; hematite is black in color, the color of the line is red-brown.

3. Transparency . The ability of a mineral to transmit light through itself. It is assessed at a qualitative level by viewing the mineral in the light. On this basis:

Transparent (quartz, Icelandic spar, crystal);

Translucent (gypsum);

Translucent at the edges (opal);

Not transparent (pyrite, hematite).

4.Glitter – the ability of minerals to reflect incident light depends on the refractive index of the mineral. The brilliance of the mineral is due to reflection from the surface of the crystal faces or fracture. Distinguish between Me and non-Me

1. Minerals with metallic and metallic luster(more than 3.0). me-reminiscent of the brilliance of fresh metal (pyrite, galena), and metallic (2.6 - 3.0) - of a tarnished metal surface (graphite, sphalerite). These lusters are inherent in opaque native metals (gold, silver, copper, etc.), many sulfur compounds (galena, chalcopyrite, etc.) and metal oxides (magnetite, pyrolusite, etc.).

2.nemee - shine. characteristic of light-coloured, often transparent minerals. Non-metallic luster varies:

Diamond. (1.9 - 2.6) The strongest brilliance is characteristic of minerals - with a high refractive index (diamond, cinnabar).

Glass. (1.3 – 1.9) Reminiscent of a sheen from a glass surface. Non-metallic luster is inherent in transparent minerals. It is typical for minerals with a low refractive index (calcite, quartz).

Fatty. Shine, as from a surface covered with a film of fat. Such brilliance is due to the mutual extinction of the reflected rays of light from the uneven surface of the mineral (nepheline, native sulfur).

Pearl. Reminiscent of the iridescent play of the mother-of-pearl surface of a sea shell. It is typical for minerals with very perfect and perfect cleavage (mica, gypsum).

Silky. Inherent in minerals with a fibrous structure. (asbestos).

Matte or dull. Minerals with a very finely rough fracture surface (flint, clay) are also observed.

Shine depends on:

Conditions of surface min-la: if the surface is not smooth, then an oily sheen (quartz), waxy sheen is observed;

Crystal forms: fibrous form, the mineral is characterized by a silky sheen.

Some minerals have different luster on the faces of crystals and on a fracture. So, for example, quartz has glassy luster on the edges, and oily luster on the break. Thin films on a stale surface and deposits of foreign substances also dramatically change the brilliance of the mineral.

5. TV - the ability of a mineral to resist external mechanical influences, scratching, grinding. is an important diagnostic feature.

There are several methods for determining hardness. In mineralogy, the Mohs scale is used. Built on the basis of reference samples, arranged in order of increasing hardness:

1 Talc Mg3(OH)2

2 Gypsum Ca*2H2O

3 Calcite Ca

4 Fluorite CaF2

5 Apatite Ca53(F, Cl)

6 Orthoclase K

7 Quartz SiO2

8 Topaz Al2(F, OH)2

9 Corundum Al2O3

The values ​​of the Mohs scale are relative and determined conditionally, by scratching. Those. quartz scratches feldspars (orthoclase), but cannot scratch topaz. The process of determining the hardness of a mineral on the Mohs scale occurs as follows: if, for example, apatite (solidity = 5) scratches the studied mineral, while the sample itself can scratch fluorite (solidity = 4), then the sample hardness is determined = 4.5.

Mohs scale standards can replace the following items: steel knife blade - hardness of about 5.5, file - about 7, plain glass - 5

6. Cleavage - the ability of mines to split or split along certain planes with the formation of a mirror-smooth surface.

Cleavage is related to the structure of the crystal and the nature of the atomic bonds. Along the cleavage planes, the bond forces are weaker than along other directions. Cleavage planes always have a high density of atoms and in all cases are parallel to possible crystal faces. Thus, the cleavage of pyroxenes and amphiboles is also directly related to their structure, which contains chains of silicon-oxygen tetrahedra.

Cleavage is identified by tracing regular crack patterns in transparent minerals such as fluorite or calcite, or even reflective planes formed by cleavage of crystals, as seen in feldspars, pyroxenes, and micas. Traces of cleavage planes play an important role as determining directions in the optical study of xenomorphic grains under a microscope, which do not have well-defined faces.

The degree of perfection of the manifestation of cleavage of the studied mineral is determined by comparing it with the data of the following 5-step scale:

very perfect– the mineral splits easily splits into flakes, plates, leaves (mica, molybdenite).

perfect- when struck with a hammer - punctures, which are a reduced likeness of a broken crystal. So, when breaking halite, small regular cubes are obtained, when crushing calcite, regular rhombohedrons (topaz, chromium diopside, fluorite, barite) are obtained. Fragments with even smooth edges are formed

average characterized by the fact that both cleavage planes and uneven fractures in random directions (feldspars, pyroxenes) are clearly observed on the fragments of crystals

imperfect smooth surfaces is found with difficulty upon careful examination of the uneven surface of the mineral cleavage (apatite, cassiterite).

Very imperfect- no smooth surfaces.

When splitting minerals that lack cleavage or have poor cleavage, irregular fracture surfaces appear, which in appearance are characterized as: conchoidal (opal), uneven (pyrite), even (wurtzite), splintery (actinolite), hooked (native silver), rough (diopside), earthy (limonite).

When processing a stone, the presence of cleavage makes it easier to obtain flat surfaces along its planes, but makes it difficult to grind and polish other planes, since cleavage cracks can occur during processing. In addition, cleavage can cause minerals to chip during use.

12. Morphology of single crystals and aggregates .

Crystal Shape (habitus);

Doubles;

Hatching of edges.

Depending on the formation conditions, the same minerals can crystallize in different forms, but the internal (crystal lattice) structure is always the same. In nature, minerals crystallize in the form of: individual single crystals, intergrowths of twins, aggregates.

Habit – appearance of crystals, m/b:

Isometric- forms equally developed in three spatial directions: octahedron, rhombohedron, cube (octahedron - diamond, rhombohedrons - diamond, cubes - barite, pyrite).

elongated- forms elongated in one spatial direction: prismatic, columnar, columnar, acicular, fibrous (tourmaline - prismatic crystals, wollastanite - acicular crystals, asbestos - fibrous).

Flat- forms elongated in two spatial directions - tabular, lamellar, scaly (mica - scaly crystals).

The shape of the crystals m / b is skeletal and dendritic (tree-like branched).

Doubles - regular intergrowths of 2 or more crystals, which are often a diagnostic sign of minerals.

Twins: intergrowths (spear-shaped - for example, dovetail) and intergrowths (staurolite - 2 hexagonal prisms grow into each other)

Polysynthetic twinning - intergrowth of many crystals (eg, plagioclase -K-Na - feldspars, carbonates)

Aggregates :

Druze - intergrowths of well-formed crystals, different in height, differently oriented, united by a common base;

brushes, crusts - aggregates, different in height;

secretions - mineral formations that fill voids in rocks. Filling occurs from the periphery to the center. If brushes appear on the surface of voids, then such formations are called geodes (amethyst, quartz);

nodules - mineral formations of a spherical shape, in which the filling of the substance goes from the center to the periphery (carbonates);

ooliths - spherical formations having a shell-like structure;

spherulites - spherical mineral formations with a radial-radiant structure (tourmaline);

dendrites - crystals with a complex tree-like branched structure (native silver);

sinter aggregates - when minerals crystallize from solutions (stalactites, stalagmites).

Aggregates m / b sinter, earthy, tree-like.

Earthy aggregates are mainly characteristic of loose, powdery minerals. These include part of the sedimentary rocks - clay (kaolin), bauxites.

Hatching on the edges - is a characteristic property of a particular mineral. Hatchings are:

Transverse parallel (in Quartz).

Longitudinal parallel (tourmaline, epidote).

Intersecting (magnetite).

13. Genesis of rocks and minerals - general, classification of processes .

Mineral formation processes:

1) Endogenous

Igneous

Postmagmatic

Pegmatite

Pneumatite

hydrothermal

2) exogenous

3) metamorphic

Endogenous processes occur inside the Earth and are associated with magmatic activity. For them, high t-ry and pressure are characteristic.

exogenous processes occur on the surface of the Earth and are associated with the transfer, redeposition, weathering, mechanical destruction of rocks and minerals.

Metamorphic processes- processes of deep transformation of previously formed rocks and minerals under the influence of high temperatures and pressure.

Magmatic processes- the highest t-stage of endogenous processes associated with the crystallization of mines from magma in the form of aggregates of igneous rocks (t ≈700˚С).

Magma- a multicomponent silicate system containing 5-10% of the gas phase.

pegmatite process- the process of crystallization of the residual magmatic melt enriched in volatile components, leading to the formation of specific rocks of a coarse-grained structure, which are called pegmatites. Har-ny for education: feldspar quartz, pegmatite veins are formed.

Pneumatite processes formation of mines from the gas phase. At some stages of magma crystallization (possible release of P, Cl, F, S). Rising to the upper layers → crystallization (during sudden cooling), minerals (sulfur, ammonia) are formed.

hydrothermal processes- hot mountain solutions released from magma, penetrating through cracks into colder parts of the Earth's crust, water vapor condenses with lateral rocks and forms hydrothermal veins. Characteristic for the formation of quartz, calcite, barite.

Hi all! Today I decided to talk about what jewelry is made of for a person. These are precious stones that are mined from the bowels of the Earth, in which minerals are found. And in this post we will talk about minerals, about the raw materials from which these beautiful jewels are made...

The earth's crust (more about the earth's crust), mainly consists of substances called -. Minerals have played a very important role in the development of mankind and the creation of civilizations.

People in the Stone Age used flint tools. A man about 10,000 years ago mastered the method of obtaining copper from ore, and with the invention of bronze (an alloy of tin and copper), a new age began - the Bronze Age.

Since the beginning of the Iron Age 3300 years ago, man has mastered more and more ways to use minerals that are mined from the earth's crust. As before, modern industry depends on the mineral resources of the Earth.

Finding new deposits requires knowledge of what they are, the ability to tell them apart, and how they ended up where we found them.

About 3,000 types of minerals are counted by scientists, but only 100 of them are quite widespread.

Minerals belong to the inorganic (non-living) world. They are most often solids. Only mercury is an exception.

organic and inorganic substances.

Everything that is mined from the earth, many call minerals. Also, they include fossil fuels, coal for example, in this category.

Mineralogists are people who study minerals professionally. They believe that oil, coal and natural gas are organic substances, because they were formed from the remains of once living animals and plants, and therefore are not minerals.

Minerals have a specific chemical composition. They are always homogeneous, in other words, all parts of the mineral are the same. They differ in this from rocks, which are composed of several minerals.

Minerals are composed of chemical elements, that is, substances that can no longer be decomposed into other substances by chemical means. In its natural form, out of 107 elements that are known to science, 90 are found in the earth's crust.

Some in the earth's crust are pure or almost pure. They are called native elements.

There are 22 native elements, among them - silver, gold and diamonds (one of the forms of carbon).

Earth's crust.

74% of the mass of the earth's crust is made up of two elements: silicon and oxygen. Another 24.27% are the other six elements: iron, aluminum, sodium, calcium, magnesium and potassium. Together they form almost 99% of the earth's crust.

The most common minerals are these are silicates, a chemical compound of silicon and oxygen, often with an admixture of one or more of the other six elements.

Silicates such as mica, quartz and feldspars are the most common. In different proportions, all three are the main components of different types of granite. Quartz eroded from granite often accumulates along the coast and forms sandy beaches.

Definition of minerals.

Common minerals such as feldspars, quartz and mica are called rock-forming minerals. This distinguishes them from minerals, which are found only in small quantities.

Another rock-forming mineral is calcite. It forms limestone rocks.

There are a lot of minerals in nature. Mineralogists have developed a whole system of their definition, which is based on chemical and physical properties.

Very simple properties, such as hardness or color, sometimes help to recognize a mineral. And sometimes this requires complex laboratory tests using reagents.

Some minerals can be recognized by color, such as malachite (green) and lapis lazuli (blue). But color is often deceptive, because in many minerals it varies quite widely.

Differences in color depend on temperature, impurities, radiation, lighting and erosion.

Mineral trait and hardness.

Mineral Trait - it is the powder that you get when you scrape a mineral. A trait is an important characteristic: it sometimes differs from the color of the mineral in the sample and is usually constant for the same mineral.

Also, minerals still differ in hardness, which is estimated on the Mohs scale (named after the Austrian mineralogist) from 1 to 10.

The soft mineral talc on it corresponds to 1, and diamond, the hardest of natural minerals, corresponds to 10.

Specific gravity.

Specific gravity, or density, is the ratio between the weight of a substance and the same amount of water. This value for the definition is quite important.

If we take the specific gravity of water as 1, then for most minerals it varies from 2.2 to 3.2. The specific gravity of some minerals (there are few of them) is very high or very low.

For example, it is wounded in graphite 1.9, and in gold from 15 to 20, depending on the purity. For the definition of minerals, another indicator is cleavage, i.e., how the mineral breaks apart when struck.

Bringing the mineral to the light, you can get information about it. Transparent minerals transmit light so easily that everything can be seen through them.

Opaque minerals do not transmit light at all, but rather reflect it or absorb it. These properties are also used during the definition process. Minerals often have an iridescent or metallic sheen.

For example, galen (lead ore) has a metallic luster, it shines almost like a metal, while most silicates have a vitreous, they resemble shiny glass.

There are also other types of brilliance - earthy (dull), pearl, silky (or satin), adamant (like a diamond). Some minerals may have several types of luster.

The luster of calcites varies from earthy to glassy. Many minerals have specific properties that make them easy to recognize. For example, talc is soapy to the touch, while arsenic, a native element and arsenic, smell like garlic when heated.

Under x-ray or ultraviolet light, some minerals fluoresce (change color or glow). Others, under pressure or when heated, are electrically charged.

There are also minerals that can only be recognized through special tests in laboratories. Some dissolve only in concentrated acids, but not in dilute ones, others only in hot acids, but not in cold ones.

Crystals.

Minerals have their own specific composition and chemical formula. Halite (rock salt) has the chemical formula NaCl. This means that halite is a chemical compound of sodium (Na) and (Cl).

So each mineral has a certain and constant composition, the atoms of its elements build the correct three-dimensional lattice of a specific structure for it.

These crystal lattices are geometric figures, their flat faces are arranged symmetrically.

If you leave a little salty water in a flat dish for a while, it will evaporate, and salt crystals will form at the bottom.

A magnifying glass shows that they are regular cubes. The study of crystals is important for the identification of minerals, since the crystals of most minerals have a regular, defined shape.

There are seven basic crystallographic, or isometric, systems, which are called syngonies. For example, turquoise belongs to the triclinic system, ruby ​​belongs to the hexagonal system, diamond belongs to the cubic system.

Each system can be described in accordance with the specifics of its symmetry - the properties that, when a crystal rotates around an axis, allows it to appear in an identical form two or more times in one complete revolution.

By the number of symmetry axes, you can determine the crystal.

precious minerals.

People in the Stone Age made jewelry from gold, in the Bronze Age - from silver. Many minerals are at the disposal of jewelers today.

Diamond (especially colorless) is the most expensive gemstone. Also, the most expensive stones include: ruby, emerald and sapphire, which, first of all, are valued for their color.

These stones are so expensive that their weight is measured in carats. One carat is equal to 200 milligrams.

Diamond is a kind of chemically pure coal and does not differ in chemical composition from the ordinary soft mineral graphite, which is familiar to us from pencils.

Diamonds are valued for their brilliance and hardness. It acquires its brilliance when cutting and polishing. The reason for this difference between graphite and diamond is that their atoms are arranged differently, they have a different internal structure.

Polymorphosis is the ability of a substance to exist in two or more forms with the same chemical composition.

For example, a rare and green variety of beryl is emerald. The most beautiful specimens are found in Colombia. The most famous rubies in the world are found in Myanmar. Fine sapphires are mined in Thailand and Sri Lanka.

Well, now, I think that when we buy precious stones for ourselves, we will know about their composition and how they are mined. And we will understand in carats, which is the value of precious stones. And we will also know how minerals are determined, in what ways their hardness is determined, etc...